JP2012163819A - Focus adjusting device and image pickup apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focus adjusting device capable of favorably adjusting a focal point.SOLUTION: The focus adjusting device includes: a pair of light receiving sensors 222a and 222b that receive a pair of luminous fluxes via an optical system having a focus adjusting optical system 32; a phase difference detecting part 32 that detects a shift length of an image surface by the optical system based on the output of the pair of light receiving sensors; a focus adjusting part 36 that adjusts the focal point of the optical system by driving the focus adjusting optical system in an optical axis direction; a starting part 28 that starts the focus adjustment by the focus adjusting part; a storage part 24 that stores the shift length detected by the focus detecting part; an exposure control part 21 that controls exposure conditions of the pair of light receiving sensors; and a control part 21 that, when the starting part starts the focus adjustment, determines whether or not allowing the exposure control part to change the exposure conditions based on the shift length stored in the storage part.

Description

  The present invention relates to a focus adjustment device and an imaging device.

  2. Description of the Related Art Conventionally, a focus adjustment device that detects a focus state of an optical system after a release button is half-pressed is known. In such a focus adjustment device, when the focus state of the optical system is detected, if the exposure is not suitable for focus detection, exposure control is performed so that the exposure is suitable for focus detection. A technique for detecting the focus state of an optical system after a suitable exposure is known (for example, Patent Document 1).

JP 2005-316271 A

  However, in the prior art, if the exposure is not suitable for focus detection after the release button is pressed halfway, the exposure control is uniformly performed so that the exposure is suitable for focus detection. There is a case where it takes time until the focus lens is driven after being half-pressed.

  The problem to be solved by the present invention is to provide a focus adjustment device capable of suitable focus adjustment.

  The present invention solves the above problems by the following means. In the following description, reference numerals corresponding to the drawings showing the embodiment of the present invention are given and described. However, the reference numerals are only for facilitating the understanding of the invention and are not intended to limit the invention. .

  [1] A focus adjusting apparatus according to the present invention is based on a pair of light receiving sensors (222a, 222b) that receive a pair of light beams via an optical system having a focus adjusting optical system, and outputs of the pair of light receiving sensors. A phase difference detection unit (21) for detecting an image plane shift amount by the optical system, and a focus adjustment unit (36) for adjusting the focus of the optical system by driving the focus adjustment optical system in the optical axis direction. ), An activation unit (28) that activates focus adjustment by the focus adjustment unit, a storage unit (24) that stores the amount of deviation detected by the focus detection unit, and exposure conditions of the pair of light receiving sensors. When the focus adjustment is activated by the exposure control unit (21) to be controlled and the activation unit, the exposure control unit determines the exposure condition based on the shift amount stored in the storage unit. Decide whether to make changes Control unit to (21), characterized in that it comprises a.

  [2] In the invention related to the focus adjustment device, the control unit (21) may include the focus out of the shift amount stored in the storage unit (24) when the focus adjustment is activated. Based on the shift amount detected before starting the adjustment, it can be configured to determine whether or not the exposure control unit (21) is to change the exposure condition.

  [3] In the invention relating to the focus adjustment device, the control unit (21) may perform the exposure control when the reliability of the shift amount detected before starting the focus adjustment is equal to or greater than a predetermined value. Based on the shift amount detected before starting the focus adjustment without causing the part (21) to change the exposure condition, the focus adjustment optical system (32) Can be configured to be driven.

  [4] In the invention related to the focus adjustment device, the control unit (21) may perform the exposure when the reliability of the shift amount detected before starting the focus adjustment is less than the predetermined value. Based on the amount of deviation detected by the phase difference detection unit (21) after the exposure unit is changed by causing the control unit (21) to change the exposure condition, the focus adjustment unit ( 36) can drive the focus adjusting optical system (32).

  [5] In the invention related to the focus adjustment apparatus, an image pickup unit (22) that picks up an image by the optical system and outputs an image signal corresponding to the picked-up image; and the image signal output by the image pickup unit And a contrast detection unit (21) for detecting a focus state of the optical system by calculating an evaluation value related to the contrast of the image by the optical system, and the pair of light receiving sensors (222a, 222b). Can be configured to be provided on the light receiving surface of the imaging unit.

  [6] In the invention related to the focus adjustment apparatus, the phase difference detection unit (21) can be configured to detect the shift amount regardless of whether or not the focus adjustment is activated. .

  [7] An imaging device according to the present invention includes the above-described focus adjustment device.

  [8] In the invention related to the imaging apparatus, the image pickup apparatus further includes mode setting means (28) capable of setting a still image shooting mode, and the control unit (21) is configured such that when the still image shooting mode is set, The exposure control unit (21) can be configured to perform processing for determining whether or not to change the exposure condition.

  According to the present invention, suitable focus adjustment can be realized.

FIG. 1 is a block diagram showing a camera according to the present embodiment. FIG. 2 is a front view showing a focus detection position on the imaging surface of the imaging device shown in FIG. FIG. 3 is a front view schematically showing the arrangement of the focus detection pixels 222a and 222b by enlarging the III part of FIG. FIG. 4 is an enlarged front view showing one of the imaging pixels 221. FIG. 5A is an enlarged front view showing one of the focus detection pixels 222a, and FIG. 5B is an enlarged front view showing one of the focus detection pixels 222b. FIG. 6 is an enlarged cross-sectional view showing one of the imaging pixels 221. FIG. 7A is an enlarged cross-sectional view showing one of the focus detection pixels 222a, and FIG. 7B is an enlarged cross-sectional view showing one of the focus detection pixels 222b. 8 is a cross-sectional view taken along line VIII-VIII in FIG. FIG. 9 is a flowchart illustrating an operation example of the camera according to the present embodiment. FIG. 10 is a flowchart showing the scan operation execution process in step S111. FIG. 11 is a diagram for explaining an operation example of the camera according to the present embodiment. FIG. 12 is a diagram for explaining an operation example of the camera according to the present embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a main part configuration diagram showing a digital camera 1 according to an embodiment of the present invention. A digital camera 1 according to the present embodiment (hereinafter simply referred to as a camera 1) includes a camera body 2 and a lens barrel 3, and the camera body 2 and the lens barrel 3 are detachably coupled by a mount unit 4. Yes.

  The lens barrel 3 is an interchangeable lens that can be attached to and detached from the camera body 2. As shown in FIG. 1, the lens barrel 3 includes a photographic optical system including lenses 31, 32, 33 and a diaphragm 34.

  The lens 32 is a focus lens, and can adjust the focal length of the photographing optical system by moving in the direction of the optical axis L1. The focus lens 32 is provided so as to be movable along the optical axis L1 of the lens barrel 3, and its position is adjusted by the focus lens drive motor 36 while its position is detected by the encoder 35.

  The specific configuration of the moving mechanism along the optical axis L1 of the focus lens 32 is not particularly limited. For example, a rotating cylinder is rotatably inserted into a fixed cylinder fixed to the lens barrel 3, a helicoid groove (spiral groove) is formed on the inner peripheral surface of the rotating cylinder, and the focus lens 32 is fixed. The end of the lens frame is fitted into the helicoid groove. Then, by rotating the rotating cylinder by the focus lens drive motor 36, the focus lens 32 fixed to the lens frame moves straight along the optical axis L1.

  As described above, the focus lens 32 fixed to the lens frame by rotating the rotary cylinder with respect to the lens barrel 3 moves straight in the direction of the optical axis L1, but the focus lens drive motor 36 as the drive source is the lens. The lens barrel 3 is provided. The focus lens drive motor 36 and the rotary cylinder are connected by a transmission composed of a plurality of gears, for example, and when the drive shaft of the focus lens drive motor 36 is driven to rotate in any one direction, it is transmitted to the rotary cylinder at a predetermined gear ratio. Then, when the rotating cylinder rotates in any one direction, the focus lens 32 fixed to the lens frame moves linearly in any direction of the optical axis L1. When the drive shaft of the focus lens drive motor 36 is rotated in the reverse direction, the plurality of gears constituting the transmission also rotate in the reverse direction, and the focus lens 32 moves straight in the reverse direction of the optical axis L1. .

  The position of the focus lens 32 is detected by the encoder 35. As described above, the position of the focus lens 32 in the direction of the optical axis L1 correlates with the rotation angle of the rotating cylinder.

  As the encoder 35 of this embodiment, an encoder that detects the rotation of a rotating disk coupled to the rotational drive of the rotating cylinder with an optical sensor such as a photo interrupter and outputs a pulse signal corresponding to the number of rotations, or a fixed cylinder And the contact point of the brush on the surface of the flexible printed wiring board provided on either one of the rotating cylinders, and the brush contact provided on the other, the amount of movement of the rotating cylinder (in either the rotational direction or the optical axis direction) A device that detects a change in the contact position according to the detection circuit using a detection circuit can be used.

  The focus lens 32 can move in the direction of the optical axis L1 from the end on the camera body side (also referred to as the closest end) to the end on the subject side (also referred to as the infinite end) by the rotation of the rotating cylinder described above. it can. Incidentally, the current position information of the focus lens 32 detected by the encoder 35 is sent to the camera control unit 21 to be described later via the lens control unit 37, and the focus lens drive motor 36 calculates the focus calculated based on this information. The driving position of the lens 32 is driven by being sent from the camera control unit 21 via the lens control unit 37.

  The diaphragm 34 is configured such that the aperture diameter around the optical axis L1 can be adjusted in order to limit the amount of light flux that passes through the photographing optical system and reaches the image sensor 22 and to adjust the blur amount. The adjustment of the aperture diameter by the diaphragm 34 is performed, for example, by sending an appropriate aperture diameter calculated in the automatic exposure mode from the camera control unit 21 via the lens control unit 37. Further, the set aperture diameter is input from the camera control unit 21 to the lens control unit 37 by a manual operation by the operation unit 28 provided in the camera body 2. The aperture diameter of the aperture 34 is detected by an aperture sensor (not shown), and the lens controller 37 recognizes the current aperture diameter.

  On the other hand, the camera body 2 is provided with an imaging element 22 that receives the light beam L1 from the photographing optical system on a planned focal plane of the photographing optical system, and a shutter 23 is provided on the front surface thereof. The image sensor 22 is composed of a device such as a CCD or CMOS, converts the received optical signal into an electrical signal, and sends it to the camera control unit 21. The captured image information sent to the camera control unit 21 is sequentially sent to the liquid crystal drive circuit 25 and displayed on the electronic viewfinder (EVF) 26 of the observation optical system, and a release button ( When (not shown) is fully pressed, the photographed image information is recorded in the memory 24 that is a recording medium. As the memory 24, any of a removable card type memory and a built-in type memory can be used. An infrared cut filter for cutting infrared light and an optical low-pass filter for preventing image aliasing noise are disposed in front of the imaging surface of the image sensor 22. Details of the structure of the image sensor 22 will be described later.

  A camera control unit 21 is provided in the camera body 2. The camera control unit 21 is electrically connected to the lens control unit 37 through an electric signal contact unit 41 provided in the mount unit 4, receives lens information from the lens control unit 37, and defocuses to the lens control unit 37. Send information such as volume and aperture diameter. The camera control unit 21 reads out the pixel output from the image sensor 22 as described above, generates image information by performing predetermined information processing on the read out pixel output as necessary, and generates the generated image information. Is output to the liquid crystal driving circuit 25 and the memory 24 of the electronic viewfinder 26. The camera control unit 21 controls the entire camera 1 such as correction of image information from the image sensor 22 and detection of a focus adjustment state and an aperture adjustment state of the lens barrel 3.

  In addition to the above, the camera control unit 21 detects the focus state of the photographic optical system by the phase detection method and the focus state of the photographic optical system by the contrast detection method based on the pixel data read from the image sensor 22. I do. A specific focus state detection method will be described later.

  The operation unit 28 is a shutter release button or an input switch for the photographer to set various operation modes of the camera 1, and switches between the auto focus mode / manual focus mode and the one shot mode / continuity even in the auto focus mode. It is possible to switch between the numeric modes. Here, the one-shot mode is a mode in which the position of the focus lens 32 once adjusted is fixed and photographing is performed at the focus lens position, whereas the continuous mode is a mode in which the position of the focus lens 32 is fixed. In this mode, the focus lens position is adjusted according to the subject. The operation unit 28 can also switch between the still image shooting mode / moving image shooting mode. Various modes set by the operation unit 28 are sent to the camera control unit 21, and the operation of the entire camera 1 is controlled by the camera control unit 21. The shutter release button includes a first switch SW1 that is turned on when the button is half-pressed and a second switch SW2 that is turned on when the button is fully pressed.

  Next, the image sensor 22 according to the present embodiment will be described.

  FIG. 2 is a front view showing the imaging surface of the image sensor 22, and FIG. 3 is a front view schematically showing the arrangement of the focus detection pixels 222a and 222b by enlarging the III part of FIG.

  As shown in FIG. 3, the imaging element 22 of the present embodiment includes a green pixel G having a color filter in which a plurality of imaging pixels 221 are two-dimensionally arranged on the plane of the imaging surface and transmit a green wavelength region. A red pixel R having a color filter that transmits a red wavelength region and a blue pixel B having a color filter that transmits a blue wavelength region are arranged in a so-called Bayer Arrangement. That is, in four adjacent pixel groups 223 (dense square lattice arrangement), two green pixels are arranged on one diagonal line, and one red pixel and one blue pixel are arranged on the other diagonal line. The image sensor 22 is configured by repeatedly arranging the pixel group 223 on the imaging surface of the image sensor 22 in a two-dimensional manner with the Bayer array pixel group 223 as a unit.

  The unit pixel group 223 may be arranged in a dense hexagonal lattice arrangement other than the dense square lattice shown in the figure. Further, the configuration and arrangement of the color filters are not limited to this, and an arrangement of complementary color filters (green: G, yellow: Ye, magenta: Mg, cyan: Cy) can also be adopted.

  FIG. 4 is an enlarged front view showing one of the imaging pixels 221, and FIG. 6 is a cross-sectional view. One imaging pixel 221 includes a micro lens 2211, a photoelectric conversion unit 2212, and a color filter (not shown), and a photoelectric conversion unit is formed on the surface of the semiconductor circuit substrate 2213 of the image sensor 22 as shown in the cross-sectional view of FIG. 2212 is built in and a microlens 2211 is formed on the surface. The photoelectric conversion unit 2212 is configured to receive an imaging light beam that passes through an exit pupil (for example, F1.0) of the photographing optical system by the micro lens 2211, and receives the imaging light beam.

  In addition, focus detection pixel rows 22a, 22b, and 22c in which focus detection pixels 222a and 222b are arranged in place of the above-described imaging pixels 221 at the center of the image pickup surface of the image pickup element 22 and three positions that are symmetrical from the center. Is provided. As shown in FIG. 3, one focus detection pixel column includes a plurality of focus detection pixels 222 a and 222 b that are alternately arranged adjacent to each other in a horizontal row (22 a, 22 c, 22 c). Yes. In the present embodiment, the focus detection pixels 222a and 222b are densely arranged without providing a gap at the position of the green pixel G and the blue pixel B of the image pickup pixel 221 arranged in the Bayer array.

  Note that the positions of the focus detection pixel rows 22a to 22c shown in FIG. 2 are not limited to the illustrated positions, and may be any one or two, or may be arranged at four or more positions. it can. In actual focus detection, the photographer manually operates the operation unit 28 from among a plurality of focus detection pixel rows 22a to 22c, and selects a desired focus detection pixel row as a focus detection position. You can also

  FIG. 5A is an enlarged front view showing one of the focus detection pixels 222a, and FIG. 7A is a cross-sectional view of the focus detection pixel 222a. FIG. 5B is an enlarged front view showing one of the focus detection pixels 222b, and FIG. 7B is a cross-sectional view of the focus detection pixel 222b. As shown in FIG. 5A, the focus detection pixel 222a includes a micro lens 2221a and a semicircular photoelectric conversion unit 2222a. As shown in the cross-sectional view of FIG. A photoelectric conversion portion 2222a is formed on the surface of the semiconductor circuit substrate 2213, and a micro lens 2221a is formed on the surface. The focus detection pixel 222b includes a micro lens 2221b and a photoelectric conversion unit 2222b as shown in FIG. 5B, and a semiconductor of the image sensor 22 as shown in a cross-sectional view of FIG. 7B. A photoelectric conversion unit 2222b is formed on the surface of the circuit board 2213, and a microlens 2221b is formed on the surface. Then, as shown in FIG. 3, these focus detection pixels 222a and 222b are alternately arranged adjacent to each other in a horizontal row, thereby forming focus detection pixel rows 22a to 22c shown in FIG.

  The photoelectric conversion units 2222a and 2222b of the focus detection pixels 222a and 222b have such a shape that the microlenses 2221a and 2221b receive light beams that pass through a predetermined region (for example, F2.8) of the exit pupil of the photographing optical system. Is done. Further, the focus detection pixels 222a and 222b are not provided with color filters, and their spectral characteristics are the total of the spectral characteristics of a photodiode that performs photoelectric conversion and the spectral characteristics of an infrared cut filter (not shown). ing. However, it may be configured to include one of the same color filters as the imaging pixel 221, for example, a green filter.

  In addition, although the photoelectric conversion units 2222a and 2222b of the focus detection pixels 222a and 222b illustrated in FIGS. 5A and 5B have a semicircular shape, the shapes of the photoelectric conversion units 2222a and 2222b are not limited thereto. Other shapes such as an elliptical shape, a rectangular shape, and a polygonal shape can also be used.

  Here, a so-called phase difference detection method for detecting the focus state of the photographing optical system based on the pixel outputs of the focus detection pixels 222a and 222b described above will be described.

  FIG. 8 is a cross-sectional view taken along the line VIII-VIII in FIG. 3. The focus detection pixels 222 a-1, 222 b-1, 222 a-2, and 222 b-2 that are arranged in the vicinity of the photographing optical axis L 1 and adjacent to each other are It shows that light beams AB1-1, AB2-1, AB1-2, and AB2-2 irradiated from the distance measuring pupils 341 and 342 of the exit pupil 34 are received, respectively. 8 illustrates only the focus detection pixels 222a and 222b that are located in the vicinity of the photographing optical axis L1, but other focus detection pixels other than the focus detection pixels illustrated in FIG. 8 are illustrated. In the same manner, the light beams emitted from the pair of distance measuring pupils 341 and 342 are respectively received.

  Here, the exit pupil 34 is an image set at a distance D in front of the microlenses 2221a and 2221b of the focus detection pixels 222a and 222b arranged on the planned focal plane of the photographing optical system. The distance D is a value uniquely determined according to the curvature and refractive index of the microlens, the distance between the microlens and the photoelectric conversion unit, and the distance D is referred to as a distance measurement pupil distance. The distance measurement pupils 341 and 342 are images of the photoelectric conversion units 2222a and 2222b respectively projected by the micro lenses 2221a and 2221b of the focus detection pixels 222a and 222b.

  In FIG. 8, the arrangement direction of the focus detection pixels 222a-1, 222b-1, 222a-2, 222b-2 coincides with the arrangement direction of the pair of distance measuring pupils 341, 342.

  As shown in FIG. 8, the microlenses 2221a-1, 2221b-1, 2221a-2, and 2221b-2 of the focus detection pixels 222a-1, 222b-1, 222a-2, and 222b-2 are photographic optical systems. Near the planned focal plane. The shapes of the photoelectric conversion units 2222a-1, 2222b-1, 2222a-2, 2222b-2 arranged behind the micro lenses 2221a-1, 2221b-1, 2221a-2, 2221b-2 are the same as the micro lenses 2221a-1, 2221b-1, 2221a-2, 2221b-2. Projected onto the exit pupil 34 separated from the lenses 2221a-1, 2221b-1, 2221a-2, 2221b-2 by the distance measurement distance D, and the projection shape forms the distance measurement pupils 341, 342.

  In other words, on the exit pupil 34 at the distance measurement distance D, the microlens and the photoelectric conversion unit in each focus detection pixel so that the projection shapes (the distance measurement pupils 341 and 342) of the photoelectric conversion unit of each focus detection pixel match. Is determined, and the projection direction of the photoelectric conversion unit in each focus detection pixel is thereby determined.

  As shown in FIG. 8, the photoelectric conversion unit 2222a-1 of the focus detection pixel 222a-1 is formed on the microlens 2221a-1 by the light beam AB1-1 that passes through the distance measuring pupil 341 and goes to the microlens 2221a-1. A signal corresponding to the intensity of the image to be output is output. Similarly, the photoelectric conversion unit 2222a-2 of the focus detection pixel 222a-2 passes through the distance measuring pupil 341, and the intensity of the image formed on the microlens 2221a-2 by the light beam AB1-2 toward the microlens 2221a-2. The signal corresponding to is output.

  Further, the photoelectric conversion unit 2222b-1 of the focus detection pixel 222b-1 passes through the distance measuring pupil 342, and the intensity of the image formed on the microlens 2221b-1 by the light beam AB2-1 directed to the microlens 2221b-1. Output the corresponding signal. Similarly, the photoelectric conversion unit 2222b-2 of the focus detection pixel 222b-2 passes through the distance measuring pupil 342, and the intensity of the image formed on the microlens 2221b-2 by the light beam AB2-2 toward the microlens 2221b-2. The signal corresponding to is output.

  Then, a plurality of the above-described two types of focus detection pixels 222a and 222b are arranged in a straight line as shown in FIG. 3, and the outputs of the photoelectric conversion units 2222a and 2222b of the focus detection pixels 222a and 222b are converted into the distance measurement pupil 341, respectively. Of the pair of images formed on the focus detection pixel row by the focus detection light fluxes that pass through each of the distance measurement pupil 341 and the distance measurement pupil 342. Data on the distribution is obtained. Then, by applying an image shift detection calculation process such as a correlation calculation process or a phase difference detection process to the intensity distribution data, an image shift amount by a so-called phase difference detection method can be detected.

  Then, a conversion calculation is performed on the obtained image shift amount according to the center-of-gravity interval of the pair of distance measuring pupils, thereby obtaining a current focal plane with respect to the planned focal plane (the focal point corresponding to the position of the microlens array on the planned focal plane) The deviation of the focal plane at the detection position, that is, the defocus amount can be obtained.

  The calculation of the image shift amount by the phase difference detection method and the calculation of the defocus amount based thereon are executed by the camera control unit 21.

  Further, the camera control unit 21 reads the output of the imaging pixel 221 of the imaging element 22 and calculates a focus evaluation value based on the read pixel output. This focus evaluation value can be obtained, for example, by extracting a high-frequency component of an image output from the imaging pixel 221 of the image sensor 22 using a high-frequency transmission filter and integrating the extracted high-frequency components to detect a focus voltage. It can also be obtained by extracting high-frequency components using two high-frequency transmission filters having different cutoff frequencies and integrating them to detect the focus voltage.

  Then, the camera control unit 21 sends a control signal to the lens control unit 37 to drive the focus lens 32 at a predetermined sampling interval (distance) to obtain a focus evaluation value at each position, and the focus evaluation value is maximum. The focus detection by the contrast detection method is performed in which the position of the focus lens 32 is determined as the in-focus position. Note that this in-focus position is obtained when, for example, when the focus evaluation value is calculated while driving the focus lens 32, the focus evaluation value rises twice and then moves down twice. Can be obtained by performing an operation such as interpolation using the focus evaluation value.

  Next, an operation example of the camera 1 according to the present embodiment will be described. FIG. 9 is a flowchart showing an operation example of the camera 1 according to the present embodiment. The following operation is started when the camera 1 is turned on. In the following, a still image shooting mode is selected, and a one-shot mode, that is, a mode in which the position of the focus lens 32 adjusted once is fixed and a mode for shooting at the focus lens position is selected. A description will be given by exemplifying.

  First, in step S101, generation of a through image by the camera control unit 21 and display of a through image by the electronic viewfinder 26 of the observation optical system are started. Specifically, an exposure operation is performed by the imaging element 22, and pixel data of the imaging pixel 221 is read by the camera control unit 21. Then, the camera control unit 21 generates a through image based on the read data, and the generated through image is sent to the liquid crystal drive circuit 25 and displayed on the electronic viewfinder 26 of the observation optical system. As a result, the user can view the moving image of the subject through the eyepiece lens 27. Note that the generation of the through image and the display of the through image are repeatedly executed at predetermined intervals.

  In step S102, the camera control unit 21 starts exposure control for generating a through image. Specifically, the camera control unit 21 calculates the luminance value Bv of the entire shooting screen based on the output of the imaging element 22, and based on the calculated luminance value Bv of the entire shooting screen, the appropriate exposure is performed on the entire shooting screen. The exposure conditions such as the imaging sensitivity Sv, the exposure time Tv, and the aperture Av are set. In addition, the camera control unit 21 stores the calculated luminance value Bv in the memory 24. The luminance value Bv stored in the memory 24 is used when performing exposure control for focus detection in step S109 described later. Note that the exposure control at the time of generating the through image is repeatedly executed at a predetermined interval. However, the interval at which the exposure control for generating the through image is performed is longer than the interval at which the generation of the through image and the display of the through image are repeated. can do. For example, the exposure control for generating the through image can be performed once while the generation of the through image and the display of the through image are repeated three times.

  In step S103, the camera control unit 21 starts defocus amount calculation processing by the phase difference detection method. In the present embodiment, the defocus amount calculation process by the phase difference detection method is performed as follows. That is, first, the image sensor 22 receives a light beam from the photographing optical system, and the camera control unit 21 performs focus detection pixels 222a and 222b constituting the three focus detection pixel rows 22a to 22c of the image sensor 22. A pair of image data corresponding to the pair of images is read out. In this case, when a specific focus detection position is selected by a manual operation of the photographer, only data from focus detection pixels corresponding to the focus detection position may be read. Then, the camera control unit 21 performs image shift detection calculation processing (correlation calculation processing) based on the read pair of image data, and images at the focus detection positions corresponding to the three focus detection pixel rows 22a to 22c. The shift amount is calculated, and the image shift amount is converted into a defocus amount.

  In step S103, the camera control unit 21 evaluates the reliability of the calculated defocus amount. In the present embodiment, the camera control unit 21 sets the reliability of the defocus amount to “high”, “medium”, “low”, and “measurement” based on, for example, the matching degree and contrast of a pair of image data. Evaluation is based on four levels, “distance impossible”. For example, when the degree of coincidence between the pair of image data is high and the reliability of the defocus amount is equal to or higher than the first determination value, the camera control unit 21 evaluates the reliability of the defocus amount as “high”. If the reliability of the defocus amount is less than the first determination value and equal to or greater than the second determination value smaller than the first determination value, the reliability of the defocus amount is “medium”. And evaluate. Furthermore, when the reliability of the defocus amount is less than the second determination value and equal to or more than the third determination value smaller than the second determination value, the camera control unit 21 determines the defocus amount. Is evaluated as “low”, and when the defocus amount reliability is less than the third determination value, the defocus amount reliability is evaluated as “distance measurement impossible”. The defocus amount thus obtained and the reliability of the defocus amount are stored in the memory 24 as defocus amount history data.

  Note that the defocus amount calculation processing by such a phase difference detection method is repeatedly performed at predetermined intervals while the operation of the camera 1 is being performed.

  In step S104, the camera control unit 21 determines whether the shutter release button provided in the operation unit 28 is half-pressed (the first switch SW1 is turned on). If the shutter release button is pressed halfway, the process proceeds to step S105. On the other hand, if the shutter release button is not half-pressed, step S104 is repeated until the shutter release button is half-pressed. That is, until the shutter release button is pressed halfway, through image generation / display, through image generation exposure control, defocus amount calculation, and defocus amount reliability evaluation are repeatedly performed.

  In subsequent steps S105 to S108, the camera control unit 21 determines whether or not the reliability of the defocus amount calculated before the shutter release button is half-pressed is “high” or “medium”. Done.

  Specifically, first, in step S105, the camera control unit 21 sets n as a predetermined parameter to 0. In step S106, the defocus amount history data stored in step S103 is referred to, and the defocus amount calculated before the shutter release button is pressed halfway and the reliability of the defocus amount correspond to the parameter n. The defocus amount and the reliability of the defocus amount are read out, and it is determined whether the reliability of the read defocus amount is “high” or “medium”. For example, when the parameter n is set to 0, the camera control unit 21 reads the defocus amount calculated immediately before the shutter release button is half-pressed and the reliability of the defocus amount, and the shutter release. It is determined whether or not the reliability of the defocus amount calculated immediately before the button is half-pressed is “high” or “medium”. Further, when the parameter n is set to 1, the camera control unit 21 determines the defocus amount calculated immediately before the defocus amount calculated immediately before the shutter release button is half-pressed and the defocus amount. The reliability of the focus amount is read, and it is determined whether or not the reliability of the read defocus amount is “high” or “medium”. Similarly, as the value of n increases, the camera control unit 21 goes back to the past and determines the defocus amount calculated n times before the defocus amount calculated immediately before the shutter release button is pressed halfway. It is determined whether the reliability is “high” or “medium”.

  If it is determined in step S106 that the reliability of the defocus amount calculated n times before the defocus amount immediately before the shutter release button is half-pressed is “high” or “medium”, If it is determined that the reliability of the defocus amount calculated n times before the defocus amount immediately before the shutter release button is half-pressed is not “high” or “medium”, the process proceeds to S112. The process proceeds to S107.

  In step S107, the camera control unit 21 determines whether the value of the parameter n is less than a predetermined number. If the value of n is less than the predetermined number, the process proceeds to step S108, 1 is added to the value of n, the process returns to step S106, and the shutter release button is half-pressed using n set in step S108. It is determined whether or not the reliability of the defocus amount calculated n times before the immediately preceding defocus amount is “high” or “medium”. On the other hand, if the value of n is greater than or equal to the predetermined number in step S107, the process proceeds to step S109.

  As described above, in steps S106 to S108, the reliability of the defocus amount calculated before half-pressing the shutter release button is determined by going back a predetermined number in order from the newly calculated defocus amount. If it is determined that the reliability of the defocus amount calculated before the shutter release button is half-pressed is “high” or “medium”, the process proceeds to step S112, while the shutter release button is half-pressed. If it is determined that the reliability of the previously calculated defocus amount is not “high” or “medium”, the process proceeds to step S109.

  In step S112, since it is determined that the reliability of the defocus amount calculated before the shutter release button is half-pressed is “high” or “medium”, the camera control unit 21 controls the AE lock (exposure condition). Processing for prohibiting the change is performed. In step S113, the focus lens 32 is driven to the in-focus position based on the defocus amount before the shutter release button is half-depressed, for which the reliability is determined to be “high” or “medium”. The lens drive amount necessary for the calculation is calculated, and the calculated lens drive amount is sent to the focus lens drive motor 36 via the lens control unit 37. Next, in step S114, the focus lens drive motor 36 drives the focus lens 32 based on the lens drive amount calculated in step S113.

  Further, as described above, the defocus amount calculation process and the defocus amount reliability evaluation process in step S102 are repeatedly performed at predetermined intervals even after the shutter release button is half-pressed. Therefore, when the reliability of the defocus amount calculated after the shutter release button is half-pressed is “high” or “medium”, the camera control unit 21 determines the lens of the focus lens 32 based on the defocus amount. The driving amount is repeatedly calculated, and the focus lens 32 is driven based on the newly calculated lens driving amount. The calculation of the lens driving amount is repeatedly executed at predetermined intervals until focus lock (processing for prohibiting driving of the focus lens 32) is performed in step S116 described later.

  Then, when the focus lens 32 is driven to the in-focus position, the process proceeds to step S115, in-focus display is performed, and then the process proceeds to step S116, where focus lock (processing for prohibiting the drive of the focus lens 32) is performed. Done. Note that the in-focus display in step S115 is performed by the electronic viewfinder 26, for example. Further, when performing the focus display, a display for notifying the user that the focus operation has been performed by the phase difference detection method may be performed together.

  On the other hand, if it is determined in steps S106 to S108 that the reliability of the defocus amount calculated before the shutter release button is half-pressed is not “high” or “medium”, the process proceeds to step S109. In step S109, exposure control for focus detection is executed by the camera control unit 21 in order to set the output of the focus detection pixels 222a and 222b to an output level suitable for focus detection. Specifically, the camera control unit 21 calculates a luminance value SpotBv in a predetermined area including the focus detection pixel rows 22a to 22c illustrated in FIG. 2, and the calculated luminance value SpotBv and the entire photographing screen calculated in step S102. ΔBv, which is the difference from the luminance value Bv, is calculated. Furthermore, the camera control unit 21 adjusts the exposure in a predetermined area including the focus detection pixel rows 22a to 22c to an exposure suitable for focus detection (for example, an exposure that is one step brighter than the appropriate exposure). Then, the calculated ΔBv is corrected to obtain ΔBv ′, and based on the corrected ΔBv ′, the exposure conditions such as the imaging sensitivity Sv, the exposure time Tv, and the aperture Av are calculated. Then, the camera control unit 21 changes the exposure condition for through image generation set in step S102 to the exposure condition for focus detection calculated in step S109, thereby changing the focus detection pixel rows 22a to 22c. The exposure in the predetermined area including the image is controlled so as to be an exposure suitable for focus detection. In step S109, it is preferable to change the imaging sensitivity Sv and the exposure time Tv with priority over the aperture Av. For example, the aperture Av can be changed when an exposure suitable for focus detection cannot be obtained with only the imaging sensitivity Sv and the exposure time Tv. In addition, if the focus detection exposure is changed to an exposure brighter than the appropriate exposure, the through image displayed at the time of focus detection may become brighter. You may control so that brightness may become dark.

  Next, in step S110, the camera control unit 21 determines whether or not the reliability of the defocus amount calculated after changing to an exposure condition suitable for focus detection is “high” or “medium”. . Here, even after changing to the exposure condition suitable for focus detection, the defocus amount calculation processing is repeatedly executed, and the pair of image data is read by the focus detection pixels 222a and 222 under the exposure condition for focus detection. Has been done. The camera control unit 21 calculates the defocus amount based on the pair of image data read out under the focus detection exposure condition, and whether the reliability of the defocus amount is “high” or “medium”. Judging. If it is determined that the reliability of the defocus amount calculated after changing to an exposure condition suitable for focus detection is “high” or “medium”, the process proceeds to step S112, and focus detection is performed in steps S112 and S113. The focus lens 32 is driven based on the defocus amount calculated after changing to an exposure condition suitable for. On the other hand, if it is determined that the reliability of the defocus amount calculated after changing to the exposure condition suitable for focus detection is not “high” or “medium”, the process proceeds to step S111.

  In step S111, the camera control unit 21 performs a scan operation execution process for executing a scan operation. Here, the scan operation is a predetermined calculation of the defocus amount and the focus evaluation value by the phase difference detection method by the camera control unit 21 while the focus lens 32 is scan-driven by the focus lens drive motor 36. Thus, the detection of the in-focus position by the phase difference detection method and the detection of the in-focus position by the contrast detection method are simultaneously performed at predetermined intervals. In the following, the scan operation execution process according to the present embodiment will be described with reference to FIG. FIG. 10 is a flowchart showing the scan operation execution process according to the present embodiment.

  First, in step S201, the camera control unit 21 performs a scan operation start process. Specifically, the camera control unit 21 sends a scan drive start command to the lens control unit 37, and the lens control unit 37 drives the focus lens drive motor 36 based on the command from the camera control unit 21 to focus. The lens 32 is scan-driven along the optical axis L1. The direction in which the scan drive is performed is not particularly limited, and the scan drive of the focus lens 32 may be performed from the infinite end to the close end, or may be performed from the close end to the infinite end. Good.

  Then, while driving the focus lens 32, the camera control unit 21 reads out a pair of image data corresponding to the pair of images from the focus detection pixels 222a and 222b of the image sensor 22 at predetermined intervals. The phase difference detection method calculates the defocus amount, evaluates the reliability of the calculated defocus amount, and drives the focus lens 32 to drive the pixel output from the imaging pixel 221 of the imaging element 22 at a predetermined interval. Reading is performed, and based on this, a focus evaluation value is calculated, thereby acquiring a focus evaluation value at a different focus lens position, thereby detecting a focus position by a contrast detection method.

  In step S202, AE lock (processing for prohibiting change of exposure conditions) is performed to prevent the exposure from being changed while the focus position is detected by the contrast detection method. In step S203, the camera control unit 21 determines whether the defocus amount has been calculated by the phase difference detection method as a result of the scanning operation. If the defocus amount can be calculated, it is determined that distance measurement is possible and the process proceeds to step S206. On the other hand, if the defocus amount cannot be calculated, it is determined that distance measurement is not possible and the process proceeds to step S204. . In step S203, even when the defocus amount can be calculated, if the reliability of the calculated defocus amount is evaluated as “low” or “range measurement impossible”, the defocus amount is calculated. As a result, it proceeds to step S204.

  In step S204, the camera control unit 21 determines whether or not the in-focus position has been detected by the contrast detection method as a result of the scanning operation. If the in-focus position can be detected by the contrast detection method, the process proceeds to step S211. If the in-focus position cannot be detected, the process proceeds to step S205.

  In step S <b> 205, the camera control unit 21 determines whether the scan operation has been performed for the entire driveable range of the focus lens 32. If the scan operation is not performed for the entire driveable range of the focus lens 32, the process returns to step S203, and steps S203 to S205 are repeated to perform the scan operation, that is, while the focus lens 32 is driven to scan. The operation of simultaneously executing the calculation of the defocus amount by the phase difference detection method and the detection of the in-focus position by the contrast detection method at predetermined intervals is continuously performed. On the other hand, if the scan operation has been completed for the entire driveable range of the focus lens 32, the process proceeds to step S215.

  As a result of executing the scanning operation, if it is determined in step S203 that the defocus amount can be calculated by the phase difference detection method, the process proceeds to step S206, and in steps S206 to S210, the calculation is performed by the phase difference detection method. A focusing operation is performed based on the defocus amount.

  That is, first, in step S206, the camera control unit 21 performs a scan operation stop process, and then proceeds to step S207. The camera control unit 21 performs a scan operation prohibition process.

  In step S208, the lens driving amount required to drive the focus lens 32 to the in-focus position is calculated from the defocus amount calculated by the phase difference detection method in step S203, and the calculated lens is calculated. The driving amount is sent to the lens driving motor 36 via the lens control unit 37. Then, the lens driving motor 36 drives the focus lens 32 to the in-focus position based on the lens driving amount calculated by the camera control unit 21.

  In the present embodiment, the controller 21 repeatedly calculates the defocus amount by the phase difference detection method while the lens drive motor 36 is driven and the focus lens 32 is driven to the in-focus position. As a result, when a new defocus amount is calculated, the control unit 21 drives the focus lens 32 based on the new defocus amount.

  When the driving of the focus lens 32 to the in-focus position is completed, the process proceeds to step S209, in-focus display is performed, and then the process proceeds to step S210, where focus lock (processing for prohibiting driving of the focus lens 32) is performed. Done. Note that the in-focus display in step S209 is performed by the electronic viewfinder 26, for example. Further, when performing the focus display, a display for notifying the user that the focus operation has been performed by the phase difference detection method may be performed together.

  As a result of executing the scanning operation, if it is determined in step S204 that the in-focus position has been detected by the contrast detection method, the process proceeds to step S211 and detected in steps S211 to S214 by the contrast detection method. Based on the in-focus position, the focus lens 32 is driven.

  That is, first, in step S211, the camera control unit 21 performs a scan operation stop process, and then proceeds to step S212. As in step S207 described above, the camera control unit 21 performs a scan operation prohibition process. It is.

  Then, the process proceeds to step S213, and a lens driving process for driving the focus lens 32 to the in-focus position is performed based on the in-focus position detected by the contrast detection method. When driving the focus lens 32 to the in-focus position based on the detection result by the contrast detection method, the focus by the phase difference detection method is completed until the drive of the focus lens 32 to the in-focus position is completed. It is preferable to prohibit the driving of the focus lens 32 based on the detection result. Thereby, the hunting phenomenon of the focus lens 32 can be suppressed.

  When the driving of the focus lens 32 to the in-focus position is completed, the process proceeds to step S214, in-focus display is performed, and then the process proceeds to step S210, where focus lock (processing for prohibiting driving of the focus lens 32) is performed. Done. Note that the in-focus display in step S214 is performed by the electronic viewfinder 26, for example. Further, when performing the in-focus display, a display for notifying the user that the in-focus operation has been performed by the contrast detection method may be performed together.

  In the scanning operation of the present embodiment, the above-described steps S203 to S205 are repeatedly executed, so that the focus lens 32 is driven to scan, the defocus amount is calculated by the phase difference detection method, and the contrast detection method is used. The detection of the focal position is simultaneously performed at a predetermined interval. Then, as a result of repeatedly executing steps S203 to S205 described above, the focus detection result by the detection method in which the defocus amount can be calculated or the in-focus position can be detected first among the phase difference detection method and the contrast detection method. The focus lens 32 is used to drive to the in-focus position. Further, as described above, in the scanning operation of the present embodiment, after determining whether or not the defocus amount can be calculated by the phase difference detection method (step S203), the in-focus position can be detected by the contrast detection method. If the phase difference detection method and the contrast detection method can calculate the defocus amount and detect the in-focus position at the same time by determining whether or not the focus position has been detected, the focus by the phase difference detection method is determined. The detection result is adopted in preference to the focus detection result by the contrast detection method.

  On the other hand, if it is determined in step S205 that the scan operation has been completed for the entire driveable range of the focus lens 32, the process proceeds to step S215. In step S215, as a result of performing the scanning operation, focus detection could not be performed by any of the phase difference detection method and the contrast detection method, so that the scanning operation end processing is performed, and then in step S216 Advancing and in-focus indication is performed. The in-focus indication is performed by the electronic viewfinder 26, for example.

  In step S217, the camera control unit 21 determines whether or not the state where the shutter release button is half-pressed (the first switch SW1 is turned on) continues. If the shutter release button is half-pressed, the process proceeds to step S218. If the shutter release button is not half-pressed, the process proceeds to step S220.

  If it is determined in step S217 that the shutter release button is half-pressed, the process proceeds to step S218, and whether or not the defocus amount can be calculated by the phase difference detection method as in step S203 described above. A determination is made. As a result, when it is determined that the defocus amount can be calculated, the process proceeds to step S219, and after processing for turning off the in-focus display is performed, the process proceeds to step S207. In steps S207 to S210, the phase difference is determined. A focusing operation based on the defocus amount calculated by the detection method is performed. On the other hand, if it is determined that the defocus amount cannot be calculated, the process returns to step S217, and steps S217 and S218 are repeatedly executed while the shutter release button is being pressed halfway. In this case, since the focus lens 32 is in a stopped state, focus detection by the contrast detection method is not performed, and only focus detection by the phase difference detection method is performed.

  On the other hand, if it is determined in step S217 that the shutter release button has not been pressed halfway, the process proceeds to step S220, and processing for turning off the in-focus display is performed.

  In this way, the scan operation execution process in step S111 is performed. Then, after the scan operation execution process in step S111 is completed, the operation of the camera 1 is also terminated.

  Next, an operation example of the camera 1 according to the present embodiment will be described with reference to FIG. FIG. 11 is a diagram for explaining an operation example of the camera 1 according to the present embodiment, and illustrates a scene where the reliability of the defocus amount before half-pressing of the shutter release button is “high” or “medium”. is doing. In FIG. 11, the reliability of the defocus amount evaluated as “high” or “medium” is represented by “◯” (the same applies to FIG. 12). Further, in FIG. 11, time is shown on the horizontal axis, and a scene in which the shutter release button is half-pressed at time t5 is illustrated. For example, when the power of the camera 1 is turned on, generation and display of a through image is started (step S101). As a result, as shown in FIG. 11, first, at time t1, accumulation of electric charges according to incident light is started in the image sensor 22, and exposure control for generating a through image is started (step S102). Further, transfer of image data corresponding to the amount of accumulated charge is started from time t2, and transfer of image data started at time t2 is completed at time t3. Based on the image data that has been transferred. Calculation of the defocus amount is started (step S103). Thereby, at the time t4, the defocus amount is calculated, the reliability of the defocus amount is evaluated, and the defocus amount and the reliability of the defocus amount are stored in the memory 24. Then, such charge accumulation, exposure control for generating a through image, image data transfer, defocus amount calculation, and defocus amount reliability evaluation are repeatedly performed at predetermined intervals.

  When the shutter release button is half-pressed at time t5 (step S104 = Yes), first, the defocus amount calculated immediately before the shutter release button is half-pressed (the defocus amount calculated at time t4 in FIG. 11). It is determined whether or not the reliability of (focus amount) is “high” or “medium” (steps S105 and S106). Here, in the example shown in FIG. 11, the reliability of the defocus amount calculated immediately before the shutter release button is half-pressed (defocus amount calculated at time t4) is “high” or “medium” ( In step S106 = Yes, it is determined that it is not necessary to perform exposure control for focus detection, exposure control for focus detection is prohibited (step S112), and the defocus amount (just before the shutter release button is half-pressed) Based on the defocus amount calculated at time t4, calculation of the lens drive amount of the focus lens 32 is started (step S113). As a result, at time t6, a lens driving amount is calculated based on the defocus amount calculated immediately before the shutter release button is half-pressed (defocus amount calculated at time t4). Based on the calculated lens driving amount. Thus, the drive of the focus lens 32 is instructed, and the drive of the focus lens 32 is started (step S114).

  In this embodiment, the defocus amount is repeatedly calculated even after the shutter release button is half-pressed, and the lens drive amount is repeatedly calculated based on the calculated defocus amount. For example, in the example shown in FIG. 11, even after the shutter release button is half-pressed, the defocus amount is calculated at time t7, and the lens drive amount is calculated at time t8. Accordingly, the lens driving amount of the focus lens 32 is updated from the lens driving amount calculated at time t6 to the lens driving amount newly calculated at time t8, and the focus lens is calculated based on the lens driving amount calculated at time t8. 32 is driven. Similarly, after time t8, the defocus amount calculation and the lens drive amount calculation are repeated until the focus lens 32 is driven to the in-focus position, and the focus is calculated based on the newly calculated lens drive amount. The lens 32 is driven. During this time, since AE lock is performed, exposure control is not performed, and the calculation of the defocus amount is repeated under certain exposure conditions.

  At time t9, when the focus lens 32 is driven to the in-focus position, the focus display is turned on (step S115), and the drive of the focus lens 32 is stopped (step S116). Note that after the focus lens 32 is driven to the in-focus position, the lens drive amount is not calculated based on the defocus amount.

  FIG. 12 is a diagram for explaining an example of the operation of the camera 1 according to the present embodiment. The reliability of the defocus amount before half-pressing of the shutter release button is “low” or “distance cannot be measured”. A scene is illustrated. In FIG. 12, the reliability of the defocus amount evaluated as “low” or “incapable distance measurement” is represented by “x”. In FIG. 12, time is shown on the horizontal axis, and a scene in which the shutter release button is half-pressed at time t14 is illustrated. In the example shown in FIG. 12, at time t11, the image sensor 22 starts accumulating charges according to incident light, and exposure control for generating a through image is started (step S102). At time t12, transfer of image data corresponding to the accumulated charges is started, and at time t13, calculation of the defocus amount is started based on the transferred image data (step S103). Thereby, at time t14, the defocus amount is calculated, and the reliability of the defocus amount is evaluated and stored in the memory 24. Then, the accumulation of charges, the transfer of image data, the calculation of the defocus amount, and the evaluation of the reliability of the defocus amount are repeated, and the time t14 and the time The defocus amount is calculated at each of t15 and time t16.

  When the shutter release button is half-pressed at time t17 (step S104 = Yes), first, the reliability of the defocus amount immediately before the shutter release button is half-pressed, that is, the defocus amount calculated at time t16. Is determined (steps S105 and S106). Here, in the example shown in FIG. 12, the reliability of the defocus amount calculated immediately before the shutter release button is half-pressed (defocus amount calculated at time t16) is not “high” or “medium”. (Step S106 = No), the reliability of the defocus amount calculated before the defocus amount immediately before the shutter release button is half-pressed (defocus amount calculated at time t16) is determined (Steps S106 to S106). S108).

  For example, in the example shown in FIG. 12, when the defocus amount is calculated to be determined two times before the defocus amount immediately before the shutter release button is half-pressed, and the reliability of the defocus amount is determined (predetermined in step S107). When the number is set to 2), first, the reliability of the defocus amount (defocus amount calculated at time t15) calculated immediately before the defocus amount immediately before the shutter release button is half-pressed. Is judged. In the example shown in FIG. 12, the reliability of the defocus amount calculated immediately before the defocus amount immediately before the shutter release button is half-pressed (defocus amount calculated at time t15) is “high” or “ Since it is not “medium” (step S106 = No), the reliability of the defocus amount calculated two times before the defocus amount immediately before the shutter release button is half-pressed (defocus amount calculated at time t14). Sex is determined (steps S106 to S108). In the example shown in FIG. 12, the reliability of the defocus amount calculated two times before the defocus amount immediately before the shutter release button is half-pressed (defocus amount calculated at time t14) is also “high” or “ Since it is not “medium” (step S106 = No, step S107 = No), it is determined that it is necessary to change to an exposure condition suitable for focus detection, and exposure control for focus detection is performed (step S109).

  At time t18, the exposure condition is changed to be suitable for focus detection, and the changed exposure condition is reflected in the charge accumulation started after time t19. That is, charge accumulation is started at an exposure condition suitable for focus detection from time t19, transfer of image data based on the charge accumulated under the changed exposure condition is terminated at time t20, and focus is focused at time t21. A defocus amount based on image data obtained under exposure conditions suitable for detection is calculated. At time t21, the reliability of the defocus amount based on image data obtained under exposure conditions suitable for focus detection is determined (step S110). Here, in the example shown in FIG. 12, the reliability of the defocus amount calculated at time t21 is determined to be “high” or “medium” (step S110 = Yes), and the focus lens is based on this defocus amount. 32 is calculated (step S113), and as a result, driving of the focus lens 32 is started at time t22 (step S114).

  As described above, in the present embodiment, when the reliability of the defocus amount calculated before the shutter release button is half-pressed is “high” or “medium”, the release calculated before the shutter release button is pressed halfway. Based on the focus amount, driving of the focus lens 32 is started. Thus, according to the present embodiment, after the shutter release button is pressed halfway, there is no need to wait for the focus lens 32 to be driven until the defocus amount is calculated. The time until the focus lens 32 is driven can be shortened.

  In the present embodiment, when the reliability of the defocus amount calculated before the shutter release button is half-pressed is “high” or “medium”, as shown in FIG. 11, the shutter release button is half-pressed. Later, the focus lens 32 starts to be driven based on the defocus amount calculated before the shutter release button is half-pressed without performing exposure control for focus detection. Therefore, in this embodiment, for example, the brightness of the entire captured image is relatively high, but the brightness of the region including the focus detection pixel rows 22a to 22c is relatively low, or the brightness of the entire captured image is relatively low. However, even when the brightness of the area including the focus detection pixel rows 22a to 22c is relatively high, the reliability of the defocus amount calculated before the shutter release button is half-pressed is “high” or “medium”. Since the defocus amount reliability is high (“high” or “medium”), it is determined that exposure control for focus detection is unnecessary, and the focus lens 32 is driven without performing exposure control for focus detection. Can start. Thus, in this embodiment, when the reliability of the defocus amount calculated before half-pressing the shutter release button is “high” or “medium”, the focus detection is performed after the shutter release button is pressed halfway. The exposure condition is changed to a suitable exposure condition, charges are accumulated under the changed exposure conditions, image data corresponding to the accumulated charges is transferred, and the time required to calculate the defocus amount based on the transferred image data is saved. Therefore, the time from when the shutter release button is pressed halfway down until the focus lens 32 is driven can be shortened.

  The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  For example, in the above-described embodiment, the lens driving amount of the focus lens 32 is calculated after the shutter release button is pressed halfway. However, the lens driving amount is calculated before the shutter release button is pressed halfway. It is good also as a structure to keep. Accordingly, it is possible to save time for calculating the lens driving amount of the focus lens 32 after the shutter release button is half-pressed. Therefore, the time from when the shutter release button is half-pressed until the focus lens 32 is driven. Time can be further reduced. Even when the driving amount of the focus lens 32 is calculated before the shutter release button is half-pressed, the drive of the focus lens 32 before the shutter release button is half-pressed is prohibited. .

  In the above-described embodiment, the reliability of the defocus amount calculated before the shutter release button is half-pressed is determined retrospectively from the newly calculated defocus amount, and the reliability is “high” or “medium”. The lens drive amount is calculated based on the defocus amount that is “”, but is not limited to this configuration. For example, among the defocus amounts calculated before the shutter release button is pressed halfway, The lens driving amount may be calculated based on the defocus amount having the highest performance.

  Furthermore, in the embodiment described above, whether or not to perform exposure control for focus detection based on the defocus amount calculated before the shutter release button is pressed halfway when the shutter release button is pressed halfway. However, for example, when a button for starting focus adjustment of the optical system is provided separately from the shutter release button, before the button for starting focus adjustment is pressed, If the button for starting focus adjustment is pressed, the defocus amount is calculated based on the defocus amount calculated before the focus adjustment button is pressed. It may be configured to determine whether to perform exposure control.

  In addition, in the above-described embodiment, the reliability of the defocus amount calculated before the defocus amount immediately before the shutter release button is half-pressed is determined retroactively by a predetermined number. For example, the reliability of the defocus amount calculated up to a predetermined time (for example, 0.1 second) before the defocus amount immediately before the shutter release button is half-pressed is determined retrospectively. It is good also as a structure.

  In the above-described embodiment, the focus detection pixels 222a and 222b of the image sensor 22 are exemplified by the configuration for detecting the focus state by the phase difference detection method. However, the configuration is not limited to this configuration, and the phase difference detection is performed. A focus detection module that detects the focus state by the method may be provided independently of the image sensor 22.

  The camera 1 of the above-described embodiment is not particularly limited. For example, the present invention is applied to other optical devices such as a digital video camera, a single-lens reflex digital camera, a lens-integrated digital camera, and a camera for a mobile phone. May be.

DESCRIPTION OF SYMBOLS 1 ... Digital camera 2 ... Camera body 21 ... Camera control part 22 ... Imaging device 221 ... Imaging pixel 222a, 222b ... Focus detection pixel 24 ... Memory 28 ... Operation part 3 ... Lens barrel 32 ... Focus lens 36 ... Focus lens drive motor 37 ... Lens control unit

Claims (8)

A pair of light receiving sensors for receiving a pair of light beams via an optical system having a focus adjusting optical system;
A phase difference detection unit that detects an image plane shift amount by the optical system based on outputs of the pair of light receiving sensors;
A focus adjustment unit that adjusts the focus of the optical system by driving the focus adjustment optical system in the optical axis direction;
An activation unit that activates focus adjustment by the focus adjustment unit;
A storage unit for storing the shift amount detected by the focus detection unit;
An exposure control unit for controlling an exposure condition of the pair of light receiving sensors;
When the focus adjustment is activated by the activation unit, it is determined whether to cause the exposure control unit to change the exposure condition based on the shift amount stored in the storage unit. And a control unit. The focus adjustment apparatus according to claim 1,
When the focus adjustment is started, the control unit is configured to perform the exposure based on the shift amount detected before starting the focus adjustment among the shift amounts stored in the storage unit. A focus adjustment apparatus that determines whether or not to change the exposure condition in a control unit. The focusing apparatus according to claim 2, wherein
When the reliability of the shift amount detected before starting the focus adjustment is equal to or greater than a predetermined value, the control unit causes the exposure control unit to change the exposure condition without changing the exposure condition. A focus adjustment device that drives the focus adjustment optical system to the focus adjustment unit based on the shift amount detected before starting the adjustment. The focus adjustment apparatus according to claim 3.
When the reliability of the deviation amount detected before starting the focus adjustment is less than the predetermined value, the control unit causes the exposure control unit to change the exposure condition, and A focus adjustment apparatus that drives the focus adjustment optical system to the focus adjustment unit based on a shift amount detected by the phase difference detection unit after the change of the condition is performed. In the focus adjustment apparatus according to any one of claims 1 to 4,
An imaging unit that captures an image by the optical system and outputs an image signal corresponding to the captured image;
A contrast detection unit that detects a focus state of the optical system by calculating an evaluation value related to the contrast of the image by the optical system based on the image signal output by the imaging unit;
The pair of light receiving sensors are provided on a light receiving surface of the image pickup unit. In the focus adjustment apparatus in any one of Claims 1-5,
The focus adjustment apparatus, wherein the phase difference detection unit detects the shift amount regardless of whether or not the focus adjustment is activated.   The imaging device provided with the focus adjustment apparatus in any one of Claims 1-6. The imaging apparatus according to claim 7,
It further comprises mode setting means capable of setting the still image shooting mode,
The image pickup apparatus, wherein the control unit performs a process of determining whether or not the exposure control unit is to change the exposure condition when the still image shooting mode is set.

Images